Pluggable transceivers are defined through multi-source agreements (MSAs). MSAs are agreements for specifications of pluggable transceivers agreed to by two or more vendors and promulgated for other vendors and network operators to utilize. MSAs allow other vendors to design transceivers to the same specifications reducing risk for vendors and operators, increasing flexibility, and accelerating the introduction of new technology. Exemplary MSAs include XFP, XPAK, XENPAK, X2, XFP-E, SFP, and SFP+. Additionally, new MSAs are emerging to address new services and advanced technology. Each MSA defines the transceiver's mechanical characteristics, management interfaces, electrical characteristics, optical characteristics, and thermal requirements. Because of MSA specifications, MSA-compliant pluggable transceivers are standardized among equipment vendors and network operators to support multiple sources for pluggable transceivers and interoperability. As such, MSA-compliant pluggable transceivers have become the dominant form of optical transmitters and receivers in the industry.
Advantageously, MSA-compliant pluggable transceivers ensure engineering re-use and compatibility between various applications and the physical media dependent transceivers. Further, equipment vendors realize streamlined manufacturing and inventory control by removing wavelength specific decisions from the manufacturing process. For example, all line cards are manufactured the same, and the pluggable transceiver module with the desired wavelength (e.g. 850 nm, 1310 nm, 1550 nm, coarse wave division multiplexed (CWDM), dense wave division multiplexed (DWDM), etc.) is plugged in as a function of the specific application or development configuration. Network operators and service providers have adopted pluggable transceivers to reduce sparing costs. Further, significant cost reductions are realized by MSA standardization of pluggable transceivers because of multiple independent manufacturing sources.
The MSA specifications tightly define the mechanical characteristics, management interfaces, electrical characteristics, optical characteristics, and thermal requirements of pluggable transceivers. Advantageously, this enables interoperability among equipment vendors of pluggable transceivers, i.e. any MSA-compatible pluggable transceiver can be used in any host system designed to the MSA specification; however, these tightly defined characteristics limit the performance of pluggable transceivers since the MSA specifications were designed to maximize density and minimize cost, and not to provide advanced optical performance. To date, pluggable transceivers such as XFP, XPAK, XENPAK, X2, XFP-E, SFP, and SFP+ have been limited to short reach (less than 80 km) point-to-point applications without the need for high performance, extended reach, or advanced optical layer OAM&P. The MSA specifications have not addressed performance enhancements to enable pluggable transceivers to extend reach beyond 80 km and to provide carrier-grade optical management and performance. Where required to extend reach and to provide carrier-grade management and performance, host devices are designed with external circuitry interfaced to pluggable transceivers or pluggable transceivers are connected to optical transponders. As such, the use of pluggable transceivers to date has been limited to intra-office connections, short reach enterprise and metro networks (less than 80 km), and connection to an optical transponder capable of extended reach typically beyond 80 km.
Due to the low-cost, high-density, and widespread deployment of pluggable transceivers, both equipment vendors and network operators recognize a need to extend the benefits of pluggable transceivers to metro, regional and core network applications to enable carrier-grade wavelength division multiplexed (WDM) transport without the need for additional equipment such as optical transponders or additional circuitry performance enhancements. Such a need also must preserve the MSA mechanical characteristics, management interfaces, electrical characteristics, optical characteristics, and thermal requirements to maintain interoperability with existing host systems.
Ethernet services are proliferating from local area network (LAN)-based services to corporate wide area network (WAN)-based services all the way to service provider backbone-based services, i.e. Ethernet is becoming the protocol of choice for all network levels. As service providers move towards Ethernet as the predominate service, there has been movement in standards to develop Carrier Ethernet including Ethernet operations, administration, and maintenance (OAM). Standards include the Metro Ethernet Forum (MEF) certifications, IEEE 802.1ag Service Layer OAM (Connectivity Fault Management), IEEE 802.3ah Ethernet in the First Mile (EFM), IEEE 802.1aj Two Port MAC Relay. As OAM is introduced in Ethernet, a requirement has emerged to “demarcate” network points to enable testing, monitoring, service level agreements (SLA), and the like.
Referring to FIG. 1, an Ethernet extension application is illustrated in a conventional network 10. The network 10 includes an access/metro network 12 connected to a core data network 14 and customer premises equipment (CPE) 16. Alternatively, the CPE 16 could also be remote central office equipment or carrier extension, and CPE 16 is shown for illustration purposes. The access/metro network 12 can include a dense wave division multiplexed (DWDM) network operated by a service provider. For example, the access/metro network 12 can include multiple interconnect optical/data network elements (NEs) 18 each configured with line cards configured to provide services, such as Ethernet. The core data network 14 can include multi-protocol label switched (MPLS) routers 20 or the like. The CPE 16 can include a customer router/switch or the like.
Here, the service provider is providing Ethernet access from the CPE 16 to the core data network 14. Conventionally, demarcation devices 22 are required between the CPE 16 and the access/metro network 12 and between the core data network 14 and the access/metro network 12. Under MEF Carrier Ethernet terminology, the demarcation devices 22 are a user network interface (UNI) or a network to network interface (NNI). The UNI and NNI are physical Ethernet interfaces operating at 10 Mbs, 100 Mbps, 1 Gbps, 10 Gbps, etc. provided by the service provider. UNI is used between a CPE and the access/metro network 12, and NNI is used between the access/metro network 12 and the core data network 14. The UNI and NNI are necessary to enable testing and monitoring of Ethernet services provided to the CPE 16 and the core data network 14. The demarcation devices 22 effectively provide separation in terms of management, alarms, physical location, and the like between networks.
For the access/metro network 12, service providers are moving towards ITU-T G.709-compliant interfaces to provide transparency and carrier-grade OAM&P of wavelength and Ethernet services. ITU-T Recommendation G.709 (Interface for the optical transport network (OTN)) is an example of a framing and data encapsulation technique. G.709 is a standardized method for managing optical wavelengths in an optical network. G.709 allows for transparency in wavelength services, improvement in optical link performance through out-of-band forward error correction (FEC), improved management through full transparency, and interoperability with other G.709 clients. G.709 defines a wrapper in which a client signal (e.g. OC-48, STM-16, OC-192, STM-64, 1 GbE, 10 GbE, etc.) is encapsulated. The G.709 wrapper includes overhead bytes for optical layer OAM&P and FEC overhead for error correction. Traditionally, G.709 signals are used in a carrier-grade network to provide robust performance and OAM&P while transporting client signals with full transparency.
Disadvantageously, the demarcation devices 22 are often 10 Gbps and 2.5 Gbps G.709 transponders or externally mounted and managed layer ½ termination devices to interface the access/metro network 12. Here, the CPE 16 requires an expensive transponder or external demarcation devices to be collocated to provide Ethernet extension from the access/metro network 12 and to provide demarcation functionality. The transponder interfaces in one direction to the access/metro network 12 utilizing G.709 framing and to the CPE 16 utilizing standard Ethernet rates. Additionally, this adds an extra layer of optical-electrical conversions requiring an interface from the transponder at the CPE 16 to the CPE 16 itself.
It would be advantageous to provide a solution for Ethernet extensions and demarcations that utilize the advantages of ITU-T G.709 without requiring extra equipment and costs.